Well it's not useful to do this,

3, else

is just

else

right?

I'd say it could be useful to document developer intent in some cases, for example to show that a case that seems to be missing is in fact not, it just happens to need the same execution path as the else case.

Why not putting intent as a comment?

Because then we will definitely at some point end up with stuff like this:

when (it) {
    1 ->
    2 ->
    3 ->
    4 ->
    // case `1` is same as else-branch
    else ->
}

And suddenly you're on your own to figure out if someone just forgot to delete the comment, or someone mistakenly added the 1-branch he thought was missing because he didn't read the statement to the end, or whatever. Documenting intent in a way that the compiler or at least the linter can help you with is always superior to comments, imo.

I agree with Robin. That was my point. don't see why I can't use else with the comma there

You don't need to repeat code! You can argue for documentation purposes, sure, but not repitition.

how can I avoid repeating code?

Replace

3, else

with

else

.

when(t) {
    1 -> "A"
    2 -> "B"
    // 3,
    else -> "C"
}

like this? this sucks honestly I prefer

when {
    t == 1 -> "A"
    t == 2 -> "B"
    t == 3,
    else -> "C"
}

at this point

The language isn't forbidding anything. You are able to achieve the behavior you want with just

else

. The opinionated part of this is: If 3 and "everything else" do the same thing, you don't have any reason to specify 3 as its own case, do you?

I literally just stated "documentation of intent" as a valid reason to specify 3 as its own case. So yes, I do have a reason. We're not writing code for computers, we're writing it for other humans as well, so just behavior is not all a language is meant to specify.

Has anyone seen a youtrack feature for this or JB discussion somewhere? I'm having trouble finding it.

No idea, we were just discussing it in this thread so far. Could move this to #language-proposals or just open a feature on youtrack if there's not one yet.

I can't imagine there isn't one. I asked this questions months ago too and got the same response. I ended up just growing into it honestly, but I think it's important for there to be a more formal spot for people to say whether or not they want this.

can you post link here if you create it?

@Daniele Segato Just click on "Channels" in the left side bar.